Transcript The Cell: An Overview

The Cell: An Overview
Basic Features of
Cell Structure and Function
 Cells
are small and are visualized using a
microscope
 Cells
have a DNA-containing central
region surrounded by cytoplasm
 Cells
occur in prokaryotic an eukaryotic
forms, each with distinctive structures and
organization
Cell Theory: Fundamental to
Life
 All
organisms are cellular
 Cell:
the smallest unit of life
 Cells
come only from preexisting cells
Examples of Cells
Fig. 5-2, p. 92
Animation: Overview of cells
Units of Measure
Fig. 5-3, p. 93
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Nucleus
Small
molecules
Atoms
Proteins
Lipids
Viruses
Mitochondria
Ribosomes Smallest
bacteria
Most
bacteria
Most plant and
animal cells
Fish egg
Bird egg
Human height
Electron microscope
Light microscope
Unaided human eye
0.1 nm
1 nm
10 nm
100 nm
1 m
10 m
100 m
7
1 mm
1 cm
0.1 m
1m
10 m
Cell size
 Link
 Amazing
cells
Think/Pair/Share
 Why
are cells small?
Surface to Volume Ratios
Fig. 5-5, p. 95
Microscopy
 Magnification

Ratio between the size of an image produced
by a microscope and its actual size
 Resolution

Ability to observe two adjacent objects as
distinct from one another
 Contrast

How different one structure looks from
another – enhanced by dyes
11
Microscopy
2
groups of microscopes based on source
of illumination

Light microscope
• Uses light for illumination
• Resolution 0.2 µm

Electron microscope
• Uses an electron beam
• Resolution 2 nm
12
Bright field microscopy
Fig. 5-4a, p. 94
Dark field microscopy
Fig. 5-4b, p. 94
Phase-contrast microscopy
Fig. 5-4c, p. 94
Electron microscope types
 Transmission



Beam of electrons transmitted through sample
Thin slices stained with heavy metals
Some electrons are scattered while others
pass through to form an image
 Scanning


electron microscopy (TEM)
electron microscopy (SEM)
Sample coated with heavy metal
Beam scans surface to make 3D image
16
Transmission electron microscopy (TEM)
Fig. 5-4d, p. 94
Scanning electron microscopy (SEM)
Fig. 5-4h, p. 94
All Cells Contain DNA
 All



cells have a central region with DNA
Stores hereditary information (connection to
evolution)
Genes are located on DNA
Proteins replicate DNA and copy information
to RNA
Cytoplasm
 Cytoplasm

Surrounds the central region
 Cytosol

Aqueous solution of cell
 Organelles

Small organized structures within cytosol
Plasma Membrane
Fig. 5-6, p. 95
Animation: Cell membranes
 Membranes
Plasma Membrane
 Plasma
 Lipid
membrane defines cytoplasm
bilayer and proteins
 Hydrophobic

Selective passage hydrophilic
 Internal
external
environment of cell different from
Amazing Cells
 link
Prokaryotes and Eukaryotes
 Prokaryotes



No boundary membrane in central region
Nucleoid
Domains: Archaea and Bacteria
 Eukaryotes



Boundary membrane in central region
True nucleus
Domain: Eukarya
Prokaryotic Cells
 Prokaryotic
cells have little or no internal
membrane structure
Prokaryotic Cell Structure
Fig. 5-7, p. 97
Animation: Typical prokaryotic cell
Prokaryotic Internal Structure
 Small,

little to no membrane structure
Cell wall & capsule
 Plasma


membrane allows metabolism
ATP in mitochondria and chloroplasts
Evolution by endosymbiosis
Prokaryotic Information Transfer
 Nucleiod


Chromatin and chromosome
Three domain system (Carl Woese)
 Ribosomes


Only organelle in common with eukaryotes
DNA messenger RNA amino acids and
proteins
Prokaryotic Mobility and
Ecology
 Many

prokaryotes have flagella
Different from eukaryotic flagella
 Prokaryotes



relatively simple
Exploit all known habitats
Vastly outnumber eukaryotes
Cycling of biological elements
Table 5-1a, p. 96
Table 5-1b, p. 96
Eukaryotic Cells
 Eukaryotic
cells have a membraneenclosed nucleus and cytoplasmic
organelles
 Nucleus
contains much more DNA than
the prokaryotic nucleoid
 Cytoplasm
has endomembrane systems
dividing cell into functional and structural
components
Eukaryotic cells

Mitochondria are the powerhouses of the cell

Microbodies carry out vital reactions that link
metabolic pathways

The cytoskeleton supports and moves cell
structures

Flagella and cilia are the propellers of eukaryotic
cells
Eukaryotic Cell Overview
 Domain

Eukarya (true nucleus)
Includes protists, fungi, plants and animals
 Eukaryotic


plasma membrane function
Regulate/recognize substances (immune
system)
Cell-to-cell binding
 Fungi,
walls
plants and many protists have cell
Video
 link
Typical Animal Cell
Fig. 5-8a, p. 99
Electron Micrograph of Animal
Cell
Fig. 5-8b, p. 99
Animation: Common eukaryotic
organelles
Video
 link
Typical Plant Cell
Fig. 5-9a, p. 100
Electron Micrograph Plant Cell
Fig. 5-9b, p. 100
Which of these organelles are
absent in plant cells?
1.
2.
3.
4.
Mitochondria
Centrioles
Peroxisomes
All of the above
25%
1
25%
25%
2
3
25%
4
Eukaryotic Nucleus
 Nuclear
envelope separates nucleus and
cytoplasm

Two membranes and nuclear pores
 Nucleoplasm

within nuclear envelope
Chromatin and chromosomes
 Nucleolus

Genes for ribosomal RNA
If you treat cells with radioactive UTP, where in the
cell would you expect the greatest concentration of
radioactivity within the first few minutes?
1.
2.
3.
4.
Rough ER
Nuclear matrix
Cytoplasm
Nucleolus
25%
1
25%
25%
2
3
25%
4
Nuclear Envelope
Fig. 5-10, p. 101
Endomembrane System
 Endomembrane




system
Connects all membranes
Synthesizes/ modifies membrane proteins
Synthesizes lipids
Detoxification
 Vesicles
exchange membrane throughout
endomembrane system

ER, Golgi, nuclear envelope, lysosomes,
vesicles, plasma membrane
Endoplasmic Reticulum
 Endoplasmic

Interconnected network of membrane with
cisternae and lumen
 Rough


reticulum (ER)
ER
Ribosomes bound to surface
Membrane-associated protein synthesis
Endoplasmic Reticulum
 Smooth


ER
No ribosomes
Synthesizes lipids and detoxifies
 Proportion
activities
rough/smooth ER reflect cell
Endoplasmic Reticulum
Fig. 5-11, p. 102
b. Smooth ER
ER lumen
Cisternae
(mitochondrion)
Smooth ER lumen
Fig. 5-11b, p. 102
Golgi Complex
 Golgi

Between rough ER and plasma membrane
 Golgi

complex stack of flattened sacs
receives and modifies proteins
Molecularly tags vesicles
 Vesicles

perform many functions
Exocytosis and endocytosis
Golgi Complex
Fig. 5-12, p. 103
Lysosomes
 Lysosomes


Vesicles from Golgi complex
Hydrolytic enzymes from ER; low pH
 Autophagy
removes nonfunctional
organelles
 Phagocytosis

digests extracellular material
Major function of immune systems
Endocytosis, Exocytosis
and Lysosomes
Fig. 5-13-14, p. 104
Vesicle Traffic
Fig. 5-15, p. 105
A membrane protein synthesized in the
rough ER may be directed to
1.
2.
3.
4.
Peroxisomes
Lysosomes
Mitochondria
All of the above
25%
1
25%
25%
2
3
25%
4
Brefeldin A is a drug that disrupts transport from
the ER to the Golgi apparatus. What other
organelles and membranes are affected?
1.
2.
3.
Lysosomes,
vacuoles, plasma
membrane
Vacuoles,
mitochondria,
plasma membrane
All organelles and
membranes
100%
1
Mitochondria
 Cellular
respiration yields ATP
 Mitochondria



Outer membrane smooth
Inner membrane folded (cristae)
Mitochondrial matrix
 Mitochondria

have two membranes
have own genome
Endosymbiosis
Mitochondria
Fig. 5-16, p. 106
Microbodies
 Microbodies


Single membrane organelles
Not part of endomembrane system
 Microbody
enzymes link biochemical
pathways
 Examples

Peroxisomes, glyoxysomes or glycosomes
Microbodies
Fig. 5-17, p. 107
Cytoskeleton
 Cytoskeleton


Maintains shape and organization
Interconnected protein fibers and tubes
 Most

prominent in animal cells
Plants and fungi also use cell walls and
central vacuole
Cytoskeleton

Network of three different types of protein filaments
 Microtubules



Intermediate filaments



Long, hollow cylindrical structures
Dynamic instability
Intermediate in size
Form twisted, ropelike structure
Actin filaments


Also known as microfilaments
Long, thin fibers
65
Cytoskeleton Examples
Fig. 5-18, p. 107
Cytoskeleton Components
 Main



elements of animal cytoskeletons
Microtubules are supportive
Intermediate fibers thinner, interconnected
with microtubules
Microfilaments thinnest
68
Cytoskeleton Components
 Each



element assembled from proteins
Microtubules from tubulin
Intermediate fibers from intermediate
filaments
Microfilaments from actins
Major Components of Cytoskeleton
Fig. 5-19, p. 108
Microtubules
 Many
microtubules originate from
centrosome



Originate from centrioles
Anchor major organelles
Microtubules provide tracks for mobile
organelles
Microtubules
 Organelle


movement by motor proteins
Vesicle attached to motor protein “walks”
along microtubule
Requires ATP
 Cytoskeleton
allows large cellular
movement

Amoeboid motion, cytoplasmic streaming, cell
division
Kinesin
Fig. 5-20a,b, p. 108
Flagellar and Ciliary Beating Patterns
Fig. 5-22, p. 110
Taxol, a drug approved for treatment of breast cancer,
prevents depolymerization of microtubules. What cellular
function that affects cancer cells more than normal cells
might taxol interfere with
1.
2.
3.
Maintaining cell
shape
Cilia or flagella
Chromosome
movements in cell
division
33%
1
?
33%
2
33%
3
Specialized Structures of Plant
Cells
 Chloroplasts
are biochemical factories
powered by sunlight
 Central
vacuoles have diverse roles in
storage, structural support, and cell growth
 Cell
walls support and protect plant cells
Chloroplasts
 Chloroplasts
have multiple membranes for
photosynthesis



Outer smooth, inner folded; stroma inside
both
Thylakoids and grana inside stroma
Endosymbiosis
 Plastids
are plant organelles that include
chloroplasts, amlyoplasts and
chromoplasts
Chloroplast Structure
Fig. 5-24, p. 111
Central Vacuoles
 Central




vacuoles
Large vesicles in plants
90% of many plant cell’s volume
Turgor pressure from water
Other functions
 Tonoplast

Membrane surrounding central vacuole
Cell Walls
 Cell



Extracellular structures
Provide structure and contain pressure
Cellulose fibers for tensile strength, other
organic molecules for compression resistance
 Two


walls
types of cells walls
Primary
Secondary
Cell Wall Structure
Fig. 5-25, p. 112
The Animal Cell Surface
 Cell
adhesion molecules organize animal
cells into tissues and organs
 Cell
junctions reinforce cell adhesions and
provide avenues of communication
 The
extracellular matrix organizes the cell
exterior
Cell Adhesion and Junctions
 Cell
adhesion molecules bind cells
together nonpermanently

Glycoproteins bind to specific molecules on
other cells
 Cell
junctions seal spaces between cells
permanently

Direct cellular communication
Functions of Cellular Junction

Anchoring junctions “weld” cells together


Tight junctions prevent small ion movement


Desmosomes and adherens
Seal spaces and fuse membranes
Gap junctions allow passage without membrane
control

Same tissue
Animal Cell Connections
Fig. 5-26, p. 114
Extracellular Matrix
 Collagen

proteins
Tensile strength and elasticity
 Proteoglycans


Interlinkage
Changes consistency (jellylike to hard and
elastic)
 Fibronectins

Connect cells via integrins
Extracellular Matrix
Fig. 5-27, p. 115
Video: Fluid mosaic model